An AMOLED panel represents an Active Matrix Organic Light Emitting Diode panel. Compared with conventional liquid crystal panels, the AMOLED panel has features such as a quicker response speed, a higher contrast ratio and a wider viewing angle.
One of packaging technologies for the AMOLED panel is to adhere a substrate to a cover plate by using laser sintering of frit. By using water blocking and oxygen blocking characteristics of the frit equivalent to those of glass, it can be guaranteed that the AMOLED panel may arrive at a lifespan up to 100,000 hours or longer.
Specifically, such packaging manner using laser sintering of frit is implemented by the following steps. A frit paste (a well-known packaging material) is attached onto a surface of glass by screen printing or nozzle coating methods in accordance with designed patterns, and then a high temperature sintering is performed to solidify the frit on the surface of glass and to make the surface of the frit flat. Next, ultraviolet (UV) curing adhesive (a well-known packaging material) applying is performed at edges of the glass or outside the frit patterns using a UV curing adhesive, and then the glass is sent to a vacuum pressing machine after completion of the UV curing adhesive applying to complete alignment and pressing actions with the substrate under a vacuum state. After the solidification of the UV curing adhesive, a closed space between the substrate and the cover plate is guaranteed. At this time, the substrate contacts tightly with the surface of the frit by the function of the vacuum. After pressing and solidification, the substrate and the cover plate are sent to a laser sintering machine. The viscosity of the frit is decreased after laser heating, and meanwhile the substrate continues to sink into the surface of the low viscosity frit under the function of the vacuum pressing force to make the contact surface enlarge and to adhere the substrate with the cover plate, thereby completing the laser sintering of the whole patterns.
FIG. 1 illustratively shows a schematic diagram of an ideal state of a packaging method using laser sintering of frit in conventional technologies. As shown in FIG. 1, reference sign 11 indicates a cover plate, reference sign 12 indicates a substrate, reference sign 13 indicates a UV curing adhesive, and reference sign 14 indicates a frit paste. When the frit paste 14 is laser-sintered, the frit paste 14 obtains energies from the laser and its viscosity is decreased. The frit paste 14 needs to be adhered to the substrate 12 within 1 to 2 seconds, and it is needed to guarantee that, before laser sintering, the substrate 12 and the surface of the frit contact tightly and a gap therebetween needs to be less than 0.1 μm. A conventional solution to the problem of the gap between the surface of the frit paste 14 and the substrate 12 is to use vacuum pressing method when packaging and pressing the substrate 12 and the cover plate 11 so as to always maintain a vacuum degree of equal to or greater than 20 kPa, which causes the substrate 12 to contact more tightly with the surface of the frit so as to meet the requirements of the gap when laser sintering is performed. A method for increasing the degree that the substrate tightly contacts with the surface of the frit is to directly increase the vacuum degree between the substrate and the cover plate.
FIG. 2 illustratively shows a schematic diagram of an actual state of a packaging method using laser sintering of frit in conventional technologies. As shown in FIG. 2, reference sign 11 indicate a cover plate, reference sign 12 indicates a substrate, reference sign 13 indicates a UV curing adhesive, and reference sign 14 indicates a frit paste. Only increasing the vacuum degree between the substrate and the cover plate will bring adverse impacts and will influence other packaging effects, and the most serious is deformation of the substrate 12 and the cover plate 11, which will leads to a Newton's Ring phenomenon. The higher the vacuum degree between the substrate 12 and the cover plate 11, the more serious the Newton's Ring phenomenon will be, and the Newton's Ring phenomenon is not allowed for an AMOLED device.
Thus, defects of the existing methods lie in the following aspects. When laser sintering is performed, the substrate 12 maintains tight contact with the surface of the frit paste 14 by the function of the vacuum pressing force. If there are defects in surface flatness of the frit paste 14, a higher vacuum pressing force is needed to make up for such defects. However, in the method for obtaining a higher vacuum pressing force, when the substrate 12 and the cover plate 11 are pressed in vacuum, the vacuum degree is needed to be increased to guarantee high vacuum in the gap between the pressed substrate 12 and the cover plate 11, but doing this is prone to cause deformation of the substrate 12 and the cover plate 11, and thereby to produce the Newton's Ring phenomenon.
In order to address the above problem, FIG. 3 illustratively shows a schematic diagram of use of supporting spacers 15 in a packaging method using laser sintering of frit in conventional technologies. As shown in FIG. 3, reference sign 11 indicates a cover plate, reference sign 12 indicates a substrate, reference sign 13 indicates a UV curing adhesive, reference sign 14 indicates a frit paste, and reference sign 15 indicates supporting spacers. With the increase of the vacuum degree, the substrate 12 and the cover plate 11 suffer from the vacuum pressing force and are deformed more seriously, which thereby causes the Newton's Ring phenomenon more serious. As to this problem, the existing method is to produce a plurality of supporting spacers 15 on the substrate (A photo spacer is usually a substance which is disposed between an upper color panel and a lower TFT panel of a TFT-LCD for keeping a certain distance, i.e., playing a supporting function; in addition, the photo spacer may make thickness distribution of the liquid crystal uniform to prevent defects of blurring in image displaying due to nonuniform thickness distribution of the liquid crystal; its advantages include high sensibility, wide engineering margin, relative high mechanical characteristic, chemical resistance, high adhesiveness and wide application range) to support the substrate and the cover plate, thereby reducing the deformation of the substrate and the cover plate. This method increases process difficulties and manufacturing and producing costs, and meanwhile puts forward a challenge to the strength of the supporting spacers 15.
It can be seen that, in the existing packaging method using a frit paste, when laser sintering is performed, since the force applied on the substrate and the cover plate is not uniform, the substrate and the cover plate are prone to be deformed, which results in the Newton's Ring phenomenon and thereby influences the yield of products. In addition, even if the supporting spacers 15 are used, the supporting spacers 15 can only alleviate the non-uniformity of the force applied on the substrate and the cover plate, but still cannot completely address the problem of non-uniformity of the force applied on the substrate and the cover plate, and production costs and process steps are increased.